Hello everyone
I am trying to ramp the input volume for one of the input busses of a stereo
mixer unit (part of an AUGraph). Although I don’t get any errors when running
my code, nothing happens at all, i.e. no audible volume changes occur. I am
unsure what I am missing. Or could it be that the parameter just cannot be
ramped at all – although it reports otherwise?
This is what I got so far:
AudioUnitParameter parameter = {
.mAudioUnit = mixerUnit,
.mParameterID = kStereoMixerParam_Volume,
.mScope = kAudioUnitScope_Input,
.mElement = busNumber
};
AudioUnitParameterInfo parameterInfo = {};
UInt32 parameterInfoSize = sizeof(AudioUnitParameterInfo);
error = AudioUnitGetProperty(parameter.mAudioUnit,
kAudioUnitProperty_ParameterInfo, parameter.mScope, parameter.mParameterID,
¶meterInfo, ¶meterInfoSize);
if (error)
{
return error;
}
AudioUnitParameterOptions parameterOptions = parameterInfo.flags;
if ((parameterOptions & kAudioUnitParameterFlag_CanRamp) !=
kAudioUnitParameterFlag_CanRamp)
{
// parameter cannot be ramped-
return paramErr;
}
AudioUnitParameterEvent parameterEvent = {
.scope = parameter.mScope,
.element = parameter.mElement,
.parameter = parameter.mParameterID,
.eventType = kParameterEvent_Ramped,
.eventValues.ramp.startBufferOffset = 0,
.eventValues.ramp.durationInFrames = durationInFrames,
.eventValues.ramp.startValue = startValue,
.eventValues.ramp.endValue = endValue
};
error = AudioUnitScheduleParameters(parameter.mAudioUnit, ¶meterEvent, 1);
Thanks for any help in advance
Benjamin
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